Rotary drier for sludge

ABSTRACT

In a rotary drier for drying sludge by drying gas within a drum during travel of said sludge from one end to the other end of said drum, a deflector is provided in the proximity of a drying gas inlet to deflect the flow direction of drying gas so that the drying gas may flow evenly within the drum, and further stirring members and blade members are mounted on a rotary shaft extending through the drum so that the sludge charged into the drum may be broken and stirred and the drying gas may be caused to swirl to form turbulent flows by said stirring members and the velocity of the drying gas flowing toward an outlet of the drum may be lowered and the concentration of the sludge particles residing in the drum may be increased by said blade members.

United States Patent [191 Okawara 1March 13, 1973 [541 ROTARY DRIER FORSLUDGE Daiji Okawara, Shizuoka, Japan 22 Filed: Nov. 30, 1971 21App1.No.: 203,264

[75] inventor:

[30] Foreign Application Priority Data Oct. 15, 1971 Japan ..46/81503[56] References Cited UNITED STATES PATENTS 2/1961 Young ..263/33 R8/1959 DeCoriolis 5/1956 Struckmann ..263/33 Goossens ..263/34 Fahlberg..263/19 A Primary ExaminerJohn J. Camby Assistant ExaminerHenry C. YuenAttorney-James E. Armstrong et a1.

[57] ABSTRACT In a rotary drier for drying sludge by drying gas within adrum during travel of said sludge from one end to the other end of saiddrum, a deflector is provided in the proximity of a drying gas inlet todeflect the flow direction of drying gas so that the drying gas may flowevenly within the drum, and further stirring members and blade membersare mounted on a rotary shaft extending through the drum so that thesludge charged into the drum may be broken and stirred and the dryinggas may be caused to swirl to form turbulent flows by said stirringmembers and the velocity of the drying gas flowing toward an outlet ofthe drum may be lowered and the concentration of the sludge particlesresiding in the drum may be increased by said blade members.

4 Claims, 4 Drawing Figures PATENTEBHAR 1 3197s SHEET 10F 4 PATEminmnamsv 3.720004 sum 3 or a FIG. 3

ROTARY DRIER FOR SLUDGE This invention relates to a rotary drier adaptedfor use in the drying of sludge.

In conventional rotary driers of the type described, use has been madeof a chain or the like to uniformly distribute sludge within a rotarydrum which tends to attach onto the inner surface of the rotary drum orform an aggregate mass at the bottom of the rotary drum particularlywhen said sludge is hard to dry. With such a construction, it is almostimpossible to break the aggregate mass of sludge and the sludge is driedas aggregated for a relatively long period of time, so that there hasbeen the disadvantage that the drying efficiency is low and theaggregate mass of sludge is discharged from the drier with the surfaceonly dried and with the interior thereof incompletely dried, as aproduct. Furthermore, since the drying gas passes through the drum notevenly, the drying efficiency has been low and unevenness has tended tooccur in the dryness of the product.

In order to obviate the above-described disadvantages of theconventional driers, in the present invention stirring members aremounted on a rotary shaft extending through the drum so as to break thesludge charged into the drum in the proximity of a sludge inlet, and adeflector is provided adjacent a drying gas inlet to deflect the flowdirection of drying gas so that the drying gas may flow evenly withinthe drum to heat the inner wall of the drum and thereby to minimize thesludge attaching to said inner wall, and further the drying gas iscaused to swirl by said stirring members to form turbulent flows so thatthe sludge may be dried efficiently even when said sludge is hard todry.

The conventional driers also had the disadvantage that, since theincompletely dried sludge particles are discharged from the drum whilebeing entrained in the drying gas, the concentration of the particlesresiding within the drum becomes low or the average residence time ofthe particles in the drum becomes short. In the present invention, blademembers are provided ad jacent the rear end of the drum, whereby thesludge particles are prevented from being discharged to the outside ofthe drum while being entrained in the drying gas and thereby theconcentration of the sludge particles residing within the drum isincreased or the average residence time of the particles in the drum isprolonged, to enhance the drying efficiency.

It is, therefore, the object of the invention to provide a rotary drierwhich is capable of drying a hard-to-dry sludge with high efficiency andis simple in construction.

According to the present invention there is provided a rotary drier forsludge, comprising a drum having a sludge inlet and a drying gas inletat one end and a drying gas and product outlet at the other end thereof,and rotatably mounted on a mounting base; elongate louver boardsprovided substantially axially on the inner surface of said drum forcarrying the sludge upwardly incident to rotation of said drum; adeflector provided in said drum close to and in confronting relationwith said drying gas inlet for deflecting the flow direction of thedrying gas supplied from said drying gas inlet into said drum andthereby to distribute the drying gas evenly within the drum; a rotaryshaft extending through said drum along an axis adjacent to the axis ofsaid drum;

stirring members mounted on said rotary shaft over the length thereofexcept for a portion close to said outlet and adapted to break and stirthe sludge charged into the drum incident to rotation of said rotaryshaft; blade members mounted on said rotary shaft adjacent said outletand adapted to lower the velocity of the drying gas flowing within saiddrum toward said outlet incident to rotation of said rotary shaft;driving means for rotating said drum and driving means for rotating saidrotary shaft.

The accompanying drawings show an embodiment of the rotary drier,according to the present invention, in

which FIG. 1 is a front elevational view, partially broken away andpartially shown in section, of the rotary drier;

FIG. 2 is a fragmentary horizontal sectional view, partially inelevation, of the inlet side of the drier shown in FIG. 1;

FIG. 3 is a perspective view of the stirring members and the blademembers mounted on the rotary shaft in the proximity of the outlet ofthe drier shown in FIG. 1; and

FIG. 4 is a fragmentary vertical sectional view, partially in elevation,showing a disc mounted on the rotary shaft for deflecting the flowdirection of drying gas supplied into the drum.

Now, a preferred embodiment of the invention will be described withreference to the drawings. Referring to the drawings and particularly toFIG. 1, a drum 1 having the outer peripheral surface lined with a heatinsulating material 21 is rotatably horizontally supported on a mountingbase 3 by means of rollers 2. The drum 1 has louver boards 4substantially axially connected to the inner peripheral surface thereof.An end plate 5 on the inlet side of the drum 1 is provided with a dryinggas inlet 6 centrally thereof which communicates with a drying gasgenerator 7. Inside of the drying gas inlet 6 is provided a deflector 8in confronting relation with said inlet, which is secured to the endplate 5 by means of a fitting 9 and by which the flow direction of thedrying gas introduced into the drum from said inlet 6 is deflected sothat the drying gas may be evenly distributed within the drum. A rotaryshaft 10 extends axially through the center of the drum 1 and fork-likestirring members 11 are mounted on the rotary shaft 10 over the lengththereof except for the rear portion, said stirring members eachconsisting of a vertical or radial rod 11a and horizontal or lateralrods 11b connected to said vertical rod 11a. These stirring members 11may be mounted such that the lateral rods 11b of the respective stirringmembers are arranged helically with respect to the rotary shaft 10, soas to provide a fan effect capable of decreasing the velocity of thedrying gas passing in the drum. In the embodiment shown, the stirringmembers adjacent an outlet 15 to be described later are arranged asdescribed above. On the rear portion of the rotary shaft 10 are mountedblade members 12 to constitute an impeller, which are also arrangedhelically with respect to said rotary shaft so as to decrease thevelocity of the drying gas passing in the drum and thereby to lengthenthe residence time of the sludge within the drum. A gear ring 13 isfixedly mounted on the outer surface of the drum 1. This gear ring 13 isin meshing engagement with a pinion 14 which is driven from an electricmotor not shown. An

exhaust funnel 16 is connected to the outlet side of the drum to coverthe outlet 15 of the drum and a dried product discharge chute 17 isprovided at the lower portion of said exhaust funnel. The end plate isalso provided with a sludge inlet 18 and a trough 19 having a sludgefeed screw 20 thereon is connected with said sludge inlet 18. The rearend of the rotary shaft has a sprocket 22 mounted thereon which isdriven from an electric motor, not shown, through a chain.

In the operation of the rotary drier constructed as described above, thedrying gas generated by the gas generator 7 and introduced into the drum1 from the drying gas inlet 6 is deflected by the deflector 8 radiallyof the drum and dispersed in the interior of said drum, and then stirredby the rotating stirring members 11. Thus, the drying gas flows in thedrum substantially uniformly at every portion of the interior of saiddrum while swirling. When a sludge is charged into the drum 1 from thesludge inlet 18 under such condition, it is carried upwardly by thelouver boards 4 and falls down from the the top to the bottom of thedrum. In this case, the aggregate sludge masses are broken and scatteredwithin the drum by the stirring members 11 and effectively brought intocontact with the drying gas. The sludge reaching the bottom of the drumis again carried upwardly by the louver boards 4. This operation isrepeated, whereby the sludge is gradually dried. By the time when thesludge reaches the mid portion of the drum 1, small particles of theincompletely dried sludge are formed which are suspended within thedrum, and the so-called short pass phenomenon occurs in which thesuspending small particles of sludge project into the exhaust funnel 16by being entrained in the drying gas. However, the blade members 12 arerotating with the rotary shaft 10 in the rear portion of the drum 1,which decreases the velocity of the drying gas flowing toward the outletof the drum 1 -to lengthen the residence time of the sludge within thedrum 1, though not preventing the discharge of the gas, so that theconcentration of the sludge particles residing within the drum 1increases and hence the drying efficiency is enhanced. The blade members12 also serve to prevent the aforesaid short pass phenomenon byrepelling the small particles of sludge backward which are collidingagainst the surfaces of said blade members in their movement toward theexhaust funnel 16. The stirring members 1 1 located adjacent the outlet15 also provide a fan effect and serve to extend the average passagetime of the sludge in the drum 1 by reducing the velocity of the dryinggas flowing toward the outlet 15. By the above described functions ofthe blade members 12 and the stirring members 11, the small particles ofsludge are retained within the drum 1 for a period of time, long enoughto be completely dried. The resultant particles of uniform size aredischarged to the outside of the drum from the outlet 15 through theexhaust funnel l6 and the chute 17.

In addition to the function described above, the blade members 12 has afunction of stirring the drying gastin the rearend portion of the drum.1 to exchange the gas passing in the upper portion and lower portion ofthe drum with each other and thereby to provide a uniform temperaturedistribution within the drum 1.

FIG. 4 shows another form of the deflector 8 which consists of a disc 23mounted on the rotary shaft 10 close to and in confronting relation withthe drying gas inlet 6 and rotated by said rotary shaft. It will beobviously understood that the disc 23 serves the same purpose as that ofthe deflector 8 described previously.

In the rotary drier of the present invention, as described above, thesludge charged into the drum is dispersed within the drum by therotation of said drum and the stirring members, and dried in that stateby the swirling turbulent flow of drying gas during its travel from oneend to the other end of the drum. Therefore, even a sludge which is hardto dry can be dried continuously automatically and yet with highefficiency.

Particularly, in the rotary drier of the invention, the sludge isuniformly dispersed within the drum by being stirred and broken by thestirring members when the sludge carried upwardly by the louver boardsfalls down to the bottom of the drum and the drying gas is caused toflow spirally within the drum by said stirring members, so thateffective contact between the sludge and the drying gas can be obtainedand uniform drying of the sludge can be achieved very efficiently, andhence the operational cost can be greatly reduced. In addition, sincethe deflector is provided in the drum adjacent the drying gas inlet todeflect the flow direction of the gas, the drying gas can be distributeduniformly within the drum and the dead angle of the gas otherwiseoccurring on the inlet side of the drum can be eliminated. Furthermore,since the blade members are provided in the rear end portion of the drumto prevent the small particles of sludge from being discharged to theoutside of the drum by being entrained in the drying gas flow, theconcentration of the sludge within the drum can be increased and theresidence time of the sludge particles within the drum can belengthened. Consequently, the volume of the drier can be reduced andhence the production cost and the installation space can be greatlydecreased.

What is claimed is:

1. A rotary drier for sludge, comprising a drum having a sludge inletand a drying gas inlet at one end and a drying gas and product outlet atthe other end thereof, and rotatably mounted on a mounting base;elongate louver boards provided substantially axially on the innersurface of said drum for carrying the sludge upwardly incident torotation of said drum; a deflector provided in said drum close to and inconfronting relation with said drying gas inlet for deflecting the flowdirection of the drying gas supplied from said drying gas inlet intosaid drum and thereby to distribute the drying gas evenly within thedrum; a rotary shaft extending through said drum along an axis adjacentto the axis of said drum; stirring members mounted on said rotary shaftover the length thereof except for a portion close to said outlet andadapted to break and stir the sludge charged into the drum incident torotation of said rotary shaft; blade members mounted on said rotaryshaft adjacent said outlet and adapted to lower the velocity of thedryinggas flowing within said drum toward said outlet incident torotation of said rotary shaft; driving means for rotating said drum anddriving means for rotating said rotary shaft.

2. A rotary drier for sludge, according to claim 1, wherein saiddeflector is a disc mounted on said rotary shaft.

5 6 3. A rotary drier for sludge, according to claim 1, stirringmembers. wherein the lateral rods of those of said stirring mem- 4 Arotary drier for Sludge, according to claim 1 bers which are located inthe proximity of said outlet are arranged helically with respect to saidrotary shaft, so that the velocity of the drying gas flowing toward 5said outlet may be decreased by the rotation of said wherein the bladesof said blade members are arranged helically with respect to said rotaryshaft.

1. A rotary drier for sludge, comprising a drum having a sludge inletand a drying gas inlet at one end and a drying gas and product outlet atthe other end thereof, and rotatably mounted on a mounting base;elongate louver boards provided substantially axially on the innersurface of said drum for carrying the sludge upwardly incident torotation of said drum; a deflector provided in said drum close to and inconfronting relation with said drying gas inlet for deflecting the flowdirection of the drying gas supplied from said drying gas inlet intosaid drum and thereby to distribute the drying gas evenly within thedrum; a rotary shaft extending through said drum along an axis adjacentto the axis of said drum; stirring members mounted on said rotary shaftover the length thereof except for a portion close to said outlet andadapted to break and stir the sludge charged into the drum incident torotation of said rotary shaft; blade members mounted on said rotaryshaft adjacent said outlet and adapted to lower the velocity of thedrying gas flowing within said drum toward said outlet incident torotation of said rotary shaft; driving means for rotating said drum anddriving means for rotating said rotary shaft.
 1. A rotary drier forsludge, comprising a drum having a sludge inlet and a drying gas inletat one end and a drying gas and product outlet at the other end thereof,and rotatably mounted on a mounting base; elongate louver boardsprovided substantially axially on the inner surface of said drum forcarrying the sludge upwardly incident to rotation of said drum; adeflector provided in said drum close to and in confronting relationwith said drying gas inlet for deflecting the flow direction of thedrying gas supplied from said drying gas inlet into said drum andthereby to distribute the drying gas evenly within the drum; a rotaryshaft extending through said drum along an axis adjacent to the axis ofsaid drum; stirring members mounted on said rotary shaft over the lengththereof except for a portion close to said outlet and adapted to breakand stir the sludge charged into the drum incident to rotation of saidrotary shaft; blade members mounted on said rotary shaft adjacent saidoutlet and adapted to lower the velocity of the drying gas flowingwithin said drum toward said outlet incident to rotation of said rotaryshaft; driving means for rotating said drum and driving means forrotating said rotary shaft.
 2. A rotary drier for sludge, according toclaim 1, wherein said deflector is a disc mounted on said rotary shaft.3. A rotary drier for sludge, according to claim 1, wherein the lateralrods of those of said stirring members which are located in theproximity of said outlet are arranged helically with respect to saidrotary shaft, so that the velocity of the drying gas flowing toward saidoutlet may be decreased by the rotation of said stirring members.